X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fpawns.cpp;h=16b00ec2fa012cbf36e75001e3811e661bc91f1a;hp=eeabcbae84df6e81ed22a5bbff8c5c1b684cb1fd;hb=94dd204c3b10ebe0e6c8df5d7c98de5ba4906cad;hpb=cc2b3ece5c5d8d1183f8526fbb0ee4e1ea7a69fe diff --git a/src/pawns.cpp b/src/pawns.cpp index eeabcbae..16b00ec2 100644 --- a/src/pawns.cpp +++ b/src/pawns.cpp @@ -1,7 +1,7 @@ /* Stockfish, a UCI chess playing engine derived from Glaurung 2.1 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) - Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad Stockfish is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -17,6 +17,7 @@ along with this program. If not, see . */ +#include #include #include "bitboard.h" @@ -26,254 +27,270 @@ namespace { + #define V Value #define S(mg, eg) make_score(mg, eg) - // Doubled pawn penalty by opposed flag and file - const Score DoubledPawnPenalty[2][8] = { - { S(13, 43), S(20, 48), S(23, 48), S(23, 48), - S(23, 48), S(23, 48), S(20, 48), S(13, 43) }, - { S(13, 43), S(20, 48), S(23, 48), S(23, 48), - S(23, 48), S(23, 48), S(20, 48), S(13, 43) }}; + // Doubled pawn penalty by file + const Score Doubled[FILE_NB] = { + S(13, 43), S(20, 48), S(23, 48), S(23, 48), + S(23, 48), S(23, 48), S(20, 48), S(13, 43) }; // Isolated pawn penalty by opposed flag and file - const Score IsolatedPawnPenalty[2][8] = { + const Score Isolated[2][FILE_NB] = { { S(37, 45), S(54, 52), S(60, 52), S(60, 52), S(60, 52), S(60, 52), S(54, 52), S(37, 45) }, { S(25, 30), S(36, 35), S(40, 35), S(40, 35), - S(40, 35), S(40, 35), S(36, 35), S(25, 30) }}; + S(40, 35), S(40, 35), S(36, 35), S(25, 30) } }; // Backward pawn penalty by opposed flag and file - const Score BackwardPawnPenalty[2][8] = { + const Score Backward[2][FILE_NB] = { { S(30, 42), S(43, 46), S(49, 46), S(49, 46), S(49, 46), S(49, 46), S(43, 46), S(30, 42) }, { S(20, 28), S(29, 31), S(33, 31), S(33, 31), - S(33, 31), S(33, 31), S(29, 31), S(20, 28) }}; + S(33, 31), S(33, 31), S(29, 31), S(20, 28) } }; - // Pawn chain membership bonus by file - const Score ChainBonus[8] = { - S(11,-1), S(13,-1), S(13,-1), S(14,-1), - S(14,-1), S(13,-1), S(13,-1), S(11,-1) - }; + // Connected pawn bonus by opposed, phalanx flags and rank + Score Connected[2][2][RANK_NB]; - // Candidate passed pawn bonus by rank - const Score CandidateBonus[8] = { - S( 0, 0), S( 6, 13), S(6,13), S(14,29), - S(34,68), S(83,166), S(0, 0), S( 0, 0) - }; + // Levers bonus by rank + const Score Lever[RANK_NB] = { + S( 0, 0), S( 0, 0), S(0, 0), S(0, 0), + S(20,20), S(40,40), S(0, 0), S(0, 0) }; - const Score PawnStructureWeight = S(233, 201); + // Unsupported pawn penalty + const Score UnsupportedPawnPenalty = S(20, 10); - #undef S - - const File ShelterFile[8] = { FILE_B, FILE_B, FILE_C, FILE_D, FILE_E, FILE_F, FILE_G, FILE_G }; + // Weakness of our pawn shelter in front of the king indexed by [rank] + const Value ShelterWeakness[RANK_NB] = + { V(100), V(0), V(27), V(73), V(92), V(101), V(101) }; - inline Value score_non_center_file(const Value v) { - return Value(v * 7 / 16); - } + // Danger of enemy pawns moving toward our king indexed by + // [no friendly pawn | pawn unblocked | pawn blocked][rank of enemy pawn] + const Value StormDanger[][RANK_NB] = { + { V( 0), V(64), V(128), V(51), V(26) }, + { V(26), V(32), V( 96), V(38), V(20) }, + { V( 0), V( 0), V(160), V(25), V(13) } }; - typedef Value V; - // Arrays are indexed by rank. Zeroth value is for when no pawn on that file. - const Value PawnShelter[8] = { V(141), V(0), V( 38), V(102), V(128), V(141), V(141), V(141) }; - const Value PawnStorm[8] = { V( 26), V(0), V(128), V( 51), V( 26), V( 0), V( 0), V( 0) }; - // We compute shelter as a penalty for the given color, but shelter is used as a bonus, so we invert it using this as the basis. - const Value PawnShelterBasis = PawnShelter[0] + score_non_center_file(PawnShelter[0]) * 2; + // Max bonus for king safety. Corresponds to start position with all the pawns + // in front of the king and no enemy pawn on the horizon. + const Value MaxSafetyBonus = V(263); - inline Score apply_weight(Score v, Score w) { - return make_score((int(mg_value(v)) * mg_value(w)) / 0x100, - (int(eg_value(v)) * eg_value(w)) / 0x100); + #undef S + #undef V + + template + Score evaluate(const Position& pos, Pawns::Entry* e) { + + const Color Them = (Us == WHITE ? BLACK : WHITE); + const Square Up = (Us == WHITE ? DELTA_N : DELTA_S); + const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW); + const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE); + + Bitboard b, p, doubled, connected; + Square s; + bool passed, isolated, opposed, phalanx, backward, unsupported, lever; + Score value = SCORE_ZERO; + const Square* pl = pos.list(Us); + const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)]; + + Bitboard ourPawns = pos.pieces(Us , PAWN); + Bitboard theirPawns = pos.pieces(Them, PAWN); + + e->passedPawns[Us] = 0; + e->kingSquares[Us] = SQ_NONE; + e->semiopenFiles[Us] = 0xFF; + e->pawnAttacks[Us] = shift_bb(ourPawns) | shift_bb(ourPawns); + e->pawnsOnSquares[Us][BLACK] = popcount(ourPawns & DarkSquares); + e->pawnsOnSquares[Us][WHITE] = pos.count(Us) - e->pawnsOnSquares[Us][BLACK]; + + // Loop through all pawns of the current color and score each pawn + while ((s = *pl++) != SQ_NONE) + { + assert(pos.piece_on(s) == make_piece(Us, PAWN)); + + File f = file_of(s); + + // This file cannot be semi-open + e->semiopenFiles[Us] &= ~(1 << f); + + // Previous rank + p = rank_bb(s - pawn_push(Us)); + + // Flag the pawn as passed, isolated, doubled, + // unsupported or connected (but not the backward one). + connected = ourPawns & adjacent_files_bb(f) & (rank_bb(s) | p); + phalanx = connected & rank_bb(s); + unsupported = !(ourPawns & adjacent_files_bb(f) & p); + isolated = !(ourPawns & adjacent_files_bb(f)); + doubled = ourPawns & forward_bb(Us, s); + opposed = theirPawns & forward_bb(Us, s); + passed = !(theirPawns & passed_pawn_mask(Us, s)); + lever = theirPawns & pawnAttacksBB[s]; + + // Test for backward pawn. + // If the pawn is passed, isolated, or connected it cannot be + // backward. If there are friendly pawns behind on adjacent files + // or if it can capture an enemy pawn it cannot be backward either. + if ( (passed | isolated | connected) + || (ourPawns & pawn_attack_span(Them, s)) + || (pos.attacks_from(s, Us) & theirPawns)) + backward = false; + else + { + // We now know that there are no friendly pawns beside or behind this + // pawn on adjacent files. We now check whether the pawn is + // backward by looking in the forward direction on the adjacent + // files, and picking the closest pawn there. + b = pawn_attack_span(Us, s) & (ourPawns | theirPawns); + b = pawn_attack_span(Us, s) & rank_bb(backmost_sq(Us, b)); + + // If we have an enemy pawn in the same or next rank, the pawn is + // backward because it cannot advance without being captured. + backward = (b | shift_bb(b)) & theirPawns; + } + + assert(opposed | passed | (pawn_attack_span(Us, s) & theirPawns)); + + // Passed pawns will be properly scored in evaluation because we need + // full attack info to evaluate passed pawns. Only the frontmost passed + // pawn on each file is considered a true passed pawn. + if (passed && !doubled) + e->passedPawns[Us] |= s; + + // Score this pawn + if (isolated) + value -= Isolated[opposed][f]; + + if (unsupported && !isolated) + value -= UnsupportedPawnPenalty; + + if (doubled) + value -= Doubled[f] / distance(s, frontmost_sq(Us, doubled)); + + if (backward) + value -= Backward[opposed][f]; + + if (connected) + value += Connected[opposed][phalanx][relative_rank(Us, s)]; + + if (lever) + value += Lever[relative_rank(Us, s)]; + } + + b = e->semiopenFiles[Us] ^ 0xFF; + e->pawnSpan[Us] = b ? int(msb(b) - lsb(b)) : 0; + + return value; } -} +} // namespace -/// PawnInfoTable::pawn_info() takes a position object as input, computes -/// a PawnInfo object, and returns a pointer to it. The result is also stored -/// in an hash table, so we don't have to recompute everything when the same -/// pawn structure occurs again. +namespace Pawns { -PawnInfo* PawnInfoTable::pawn_info(const Position& pos) const { +/// init() initializes some tables used by evaluation. Instead of hard-coded +/// tables, when makes sense, we prefer to calculate them with a formula to +/// reduce independent parameters and to allow easier tuning and better insight. - Key key = pos.pawn_key(); - PawnInfo* pi = probe(key); +void init() +{ + static const int Seed[RANK_NB] = { 0, 6, 15, 10, 57, 75, 135, 258 }; + + for (int opposed = 0; opposed <= 1; ++opposed) + for (int phalanx = 0; phalanx <= 1; ++phalanx) + for (Rank r = RANK_2; r < RANK_8; ++r) + { + int bonus = Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0); + Connected[opposed][phalanx][r] = make_score(bonus / 2, bonus >> opposed); + } +} - // If pi->key matches the position's pawn hash key, it means that we - // have analysed this pawn structure before, and we can simply return - // the information we found the last time instead of recomputing it. - if (pi->key == key) - return pi; - // Initialize PawnInfo entry - pi->key = key; - pi->passedPawns[WHITE] = pi->passedPawns[BLACK] = 0; - pi->kingSquares[WHITE] = pi->kingSquares[BLACK] = SQ_NONE; - pi->halfOpenFiles[WHITE] = pi->halfOpenFiles[BLACK] = 0xFF; +/// probe() takes a position as input, computes a Entry object, and returns a +/// pointer to it. The result is also stored in a hash table, so we don't have +/// to recompute everything when the same pawn structure occurs again. - // Calculate pawn attacks - Bitboard wPawns = pos.pieces(PAWN, WHITE); - Bitboard bPawns = pos.pieces(PAWN, BLACK); - pi->pawnAttacks[WHITE] = ((wPawns << 9) & ~FileABB) | ((wPawns << 7) & ~FileHBB); - pi->pawnAttacks[BLACK] = ((bPawns >> 7) & ~FileABB) | ((bPawns >> 9) & ~FileHBB); +Entry* probe(const Position& pos, Table& entries) { - // Evaluate pawns for both colors and weight the result - pi->value = evaluate_pawns(pos, wPawns, bPawns, pi) - - evaluate_pawns(pos, bPawns, wPawns, pi); + Key key = pos.pawn_key(); + Entry* e = entries[key]; - pi->value = apply_weight(pi->value, PawnStructureWeight); + if (e->key == key) + return e; - return pi; + e->key = key; + e->value = evaluate(pos, e) - evaluate(pos, e); + return e; } -/// PawnInfoTable::evaluate_pawns() evaluates each pawn of the given color +/// Entry::shelter_storm() calculates shelter and storm penalties for the file +/// the king is on, as well as the two adjacent files. template -Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns, - Bitboard theirPawns, PawnInfo* pi) { +Value Entry::shelter_storm(const Position& pos, Square ksq) { const Color Them = (Us == WHITE ? BLACK : WHITE); + const Bitboard Edges = (FileABB | FileHBB) & (Rank2BB | Rank3BB); - Bitboard b; - Square s; - File f; - Rank r; - bool passed, isolated, doubled, opposed, chain, backward, candidate; - Score value = SCORE_ZERO; - const Square* pl = pos.piece_list(Us, PAWN); + Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, rank_of(ksq)) | rank_bb(ksq)); + Bitboard ourPawns = b & pos.pieces(Us); + Bitboard theirPawns = b & pos.pieces(Them); + Value safety = MaxSafetyBonus; + File kf = std::max(FILE_B, std::min(FILE_G, file_of(ksq))); - // Loop through all pawns of the current color and score each pawn - while ((s = *pl++) != SQ_NONE) + for (File f = kf - File(1); f <= kf + File(1); ++f) { - assert(pos.piece_on(s) == make_piece(Us, PAWN)); - - f = file_of(s); - r = rank_of(s); - - // This file cannot be half open - pi->halfOpenFiles[Us] &= ~(1 << f); - - // Our rank plus previous one. Used for chain detection - b = rank_bb(r) | rank_bb(Us == WHITE ? r - Rank(1) : r + Rank(1)); - - // Flag the pawn as passed, isolated, doubled or member of a pawn - // chain (but not the backward one). - passed = !(theirPawns & passed_pawn_mask(Us, s)); - doubled = ourPawns & squares_in_front_of(Us, s); - opposed = theirPawns & squares_in_front_of(Us, s); - isolated = !(ourPawns & adjacent_files_bb(f)); - chain = ourPawns & adjacent_files_bb(f) & b; - - // Test for backward pawn - backward = false; - - // If the pawn is passed, isolated, or member of a pawn chain it cannot - // be backward. If there are friendly pawns behind on adjacent files - // or if can capture an enemy pawn it cannot be backward either. - if ( !(passed | isolated | chain) - && !(ourPawns & attack_span_mask(Them, s)) - && !(pos.attacks_from(s, Us) & theirPawns)) - { - // We now know that there are no friendly pawns beside or behind this - // pawn on adjacent files. We now check whether the pawn is - // backward by looking in the forward direction on the adjacent - // files, and seeing whether we meet a friendly or an enemy pawn first. - b = pos.attacks_from(s, Us); - - // Note that we are sure to find something because pawn is not passed - // nor isolated, so loop is potentially infinite, but it isn't. - while (!(b & (ourPawns | theirPawns))) - Us == WHITE ? b <<= 8 : b >>= 8; - - // The friendly pawn needs to be at least two ranks closer than the - // enemy pawn in order to help the potentially backward pawn advance. - backward = (b | (Us == WHITE ? b << 8 : b >> 8)) & theirPawns; - } - - assert(opposed | passed | (attack_span_mask(Us, s) & theirPawns)); - - // A not passed pawn is a candidate to become passed if it is free to - // advance and if the number of friendly pawns beside or behind this - // pawn on adjacent files is higher or equal than the number of - // enemy pawns in the forward direction on the adjacent files. - candidate = !(opposed | passed | backward | isolated) - && (b = attack_span_mask(Them, s + pawn_push(Us)) & ourPawns) != 0 - && popcount(b) >= popcount(attack_span_mask(Us, s) & theirPawns); - - // Passed pawns will be properly scored in evaluation because we need - // full attack info to evaluate passed pawns. Only the frontmost passed - // pawn on each file is considered a true passed pawn. - if (passed && !doubled) - pi->passedPawns[Us] |= s; - - // Score this pawn - if (isolated) - value -= IsolatedPawnPenalty[opposed][f]; - - if (doubled) - value -= DoubledPawnPenalty[opposed][f]; - - if (backward) - value -= BackwardPawnPenalty[opposed][f]; - - if (chain) - value += ChainBonus[f]; - - if (candidate) - value += CandidateBonus[relative_rank(Us, s)]; + b = ourPawns & file_bb(f); + Rank rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1; + + b = theirPawns & file_bb(f); + Rank rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1; + + if ( (Edges & make_square(f, rkThem)) + && file_of(ksq) == f + && relative_rank(Us, ksq) == rkThem - 1) + safety += 200; + else + safety -= ShelterWeakness[rkUs] + + StormDanger[rkUs == RANK_1 ? 0 : + rkThem != rkUs + 1 ? 1 : 2][rkThem]; } - return value; -} -template -int computePawnShelter(const Position &pos, Square ksq) { - const Color Them = (Us == WHITE ? BLACK : WHITE); - const File kingFile = ShelterFile[file_of(ksq)]; - const Bitboard ourPawns = pos.pieces(PAWN, Us) & in_front_bb(Us, ksq); - const Bitboard theirPawns = pos.pieces(PAWN, Them) & (RankBB[rank_of(ksq)] | in_front_bb(Us, ksq)); - - int shelter = 0; - - // Compute king shelter and storm values for the file the king is on, as well as the two adjacent files. - for (int fileOffset = -1; fileOffset <= 1; fileOffset++) { - // Shelter takes full penalty for center file, otherwise it's half penalty - Bitboard shelterFile = ourPawns & FileBB[kingFile + fileOffset]; - Rank shelterClosest = shelterFile ? relative_rank(shelterFile) - : RANK_1; - - shelter += fileOffset == 0 ? PawnShelter[shelterClosest] - : score_non_center_file(PawnShelter[shelterClosest]); - - // Storm takes full penalty, unless there is an enemy pawn blocking us - Bitboard stormFile = theirPawns & FileBB[kingFile + fileOffset]; - Rank stormClosest = stormFile ? relative_rank(stormFile) - : RANK_1; - - shelter += shelterClosest + 1 == stormClosest ? PawnStorm[stormClosest] / 2 - : PawnStorm[stormClosest]; - } - - return shelter; + return safety; } -/// PawnInfo::updateShelter() calculates and caches king shelter. It is called -/// only when king square changes, about 20% of total king_shelter() calls. -template -Score PawnInfo::updateShelter(const Position& pos, Square ksq) { - int shelter = 0; - if (relative_rank(Us, ksq) <= RANK_4) - { - shelter = computePawnShelter(pos, ksq); - if (pos.can_castle(Us == WHITE ? WHITE_OO : BLACK_OO)) - shelter = std::min(shelter, computePawnShelter(pos, relative_square(Us, SQ_G1))); - if (pos.can_castle(Us == WHITE ? WHITE_OOO : BLACK_OOO)) - shelter = std::min(shelter, computePawnShelter(pos, relative_square(Us, SQ_C1))); - shelter = PawnShelterBasis - shelter; - } +/// Entry::do_king_safety() calculates a bonus for king safety. It is called only +/// when king square changes, which is about 20% of total king_safety() calls. + +template +Score Entry::do_king_safety(const Position& pos, Square ksq) { kingSquares[Us] = ksq; - kingShelters[Us] = make_score(shelter, 0); - return kingShelters[Us]; + castlingRights[Us] = pos.can_castle(Us); + minKingPawnDistance[Us] = 0; + + Bitboard pawns = pos.pieces(Us, PAWN); + if (pawns) + while (!(DistanceRingsBB[ksq][minKingPawnDistance[Us]++] & pawns)) {} + + if (relative_rank(Us, ksq) > RANK_4) + return make_score(0, -16 * minKingPawnDistance[Us]); + + Value bonus = shelter_storm(pos, ksq); + + // If we can castle use the bonus after the castling if it is bigger + if (pos.can_castle(MakeCastling::right)) + bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_G1))); + + if (pos.can_castle(MakeCastling::right)) + bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_C1))); + + return make_score(bonus, -16 * minKingPawnDistance[Us]); } // Explicit template instantiation -template Score PawnInfo::updateShelter(const Position& pos, Square ksq); -template Score PawnInfo::updateShelter(const Position& pos, Square ksq); +template Score Entry::do_king_safety(const Position& pos, Square ksq); +template Score Entry::do_king_safety(const Position& pos, Square ksq); + +} // namespace Pawns